1. Field of the Invention
This invention relates to a predictive coding system which achieves highly efficient coding of video signals as of commercial television or video telephone by making use of high correlation between adjacent picture elements in a picture.
2. Description of the Prior Art
In existing standard television a picture consists of frames which are sent by steps of thirty per second, and in each frame, interlaced scanning takes place every other scanning line; therefore each frame is composed of two consecutive fields. The elements forming the picture are called "picture elements", but since digital processing is here taken into consideration, each extracted sample will hereinafter be referred to as a picture element. Accordingly, in this case, the position of each picture element in the picture is dependent upon the sampling frequency necessary for signal digitalization.
Conventional inter-field predictive coding systems and conventional intra-field predictive coding systems have the same merits but the former has a defect of lowered coding efficiency of a moving picture and the latter a defect of insufficient coding efficiency in a still picture; therefore it is impossible to realize a coding device which achieves constant high coding efficiency in both cases of moving and stationary pictures.